My father recently retired from the heating, ventilation and air conditioning business, after more than 45 years of work in that field. He had a career at Carrier and another at Siemens. At their retirement party, there was a group of friends from the industry, some with experience from the early days of the industry's origin. One of these old friends had been a mechanic for the past 60 years, working most of the time with centrifugal coolers. They both had a great time, remembering the old days.
After retiring, I helped Dad clean the basement of the house. In more than 45 years you can accumulate a lot of materials and my father rarely threw anything away. The basement had mountains of old technical literature especially from centrifugal coolers. Most of the chillers listed in the manuals have been taken out of service in the last 10 or 15 years ("Dad, these machines haven't been manufactured in 50 years, it's probably not a problem to scrap the manual.") It occurred to me as I reviewed the literature that an "era" was going on and I knew very little about the history of one of the most important advances of the 20th century: the centrifugal cooler. Centrifugal chillers and the refrigeration industry were pushed forward by the desire of many other industries to do something better, faster, or cheaper.
In 1901, the Buffalo Forge Company in N.Y. hired a 24-year-old engineer, a graduate of Cornell University and named Willis Carrier, to work on the installation and design of heating systems. In less than a year he was in charge of the experimental engineering group. This group was the heart of the team that would form the Carrier Engineering company. It was there, in 1902 that the first project was credited to the lithographic and advertising firm Sakett-Williams in Brooklyn, New York, which has been identified by many as the first consolidated air conditioning project. (The definition of air conditioning considered the control of air temperature and humidity.) He received his first patent in 1906 for "air treatment apparatus".
The term "air conditioning" was currently coined by Stuart H. Cramer. He used the phrase in 1906, in the patent application for an artifact that added water vapor to the air in textile plants. He used the air to condition the yarn. To understand where the chiller originated, we must understand the level of engineering at that time. At the end of the nineteenth century, air conditioners did not exist. The concept of finned tubes had not yet been developed. The fans were little less than motorized windmills. Ammonia was the most common refrigerant (none of the fluorinated carbon refrigerants had yet been invented). There were no suppliers of components for refrigeration equipment.
Everything was manufactured against order of orders. Buffalo Forge had created the Carrier Air Conditioning Company. Buffalo Forge management used the young engineer's name for their new branch, instead of using their own name in that division. They thought that if this new field did not find a future or suffered tremendous failure, the name Buffalo Forge would not suffer adverse consequences. At the beginning of World War I, Buffalo Forge made the decision not to continue in the air conditioning market. The group left and formed the Carrier Engineering Corporation of America. This group was responsible for many discoveries that we take for granted today. The concept of relative humidity with respect to temperature was not fully understood. At the time, they knew that if cold water was atomized directly into a stream of hot, moist air, the result was cooling and dehumidification of the air. It was not known why this phenomenon occurred and in what proportion it did so. A lot of research was required on this. Many pioneers, in addition to Carrier and its team, were responsible for the first foundations of refrigeration and air conditioning. Although Carrier was credited with inventing air conditioning in 1902, others had concurrent patents for air treatment and cooling at the time. Many engineers and hobbyists worked in that field, Cramer had been working on cooling and humidifying spinning mills for several years. However, credit belongs primarily to this group of engineers for the practical centrifugal water chiller.
Usually, technical innovation cannot be pointed to a single moment. When Alexander Graham Bell invented the telephone and made the famous so-called "Watson come here", between two rooms, there were many people involved. Without batteries, wires, magnets, the telegraph and speaker cones and microphone, Bell would never have uttered those words. Their discovery developed from concept to hypothesis to experimentation and collaboration, until all the pieces came together and the phone worked. He used existing technology for his new invention, the same happened with the centrifugal cooler.
DESIGN
Carrier and his team did not invent the centrifugal compressor but it was a new technology by 1910. The first patents for centrifugal compressors already existed when Carrier and his team began work on their application to refrigeration. Multistage fans were already manufactured by various manufacturers, of course, centrifugal pumps were common at that time. Between 1910 and 1915, Maurice LeBlanc, working in France experimented in refrigeration and its design of the centrifugal compressor. He used carbon tetrachloride in one experiment and water vapor in another. Coal tetrachloride broke down and ruined the compressor, while water vapor could not be used because of the speeds required in the impeller. There was no technology to manufacture and operate a light high-speed pulse for water vapor. However, he was the first person to use the centrifugal compressor for a refrigeration application. LeBlanc also had problems with the shaft seals. This was a common problem even for Carrier.
According to a brief by Walter A. Grant (a Carrier employee) in October 1942, Willis Carrier's concept of "centrifugal cooler" was influenced by Taylor's hydraulic air compressor. This type of compressor encloses air on a movable column of water and compresses it at the bottom of the water column, the weight of the water is the "compressor". Carrier and his team began to study static charge, gravity and pressures as well as the theoretical concept of placing the evaporator much higher than the condenser. The concept was that the coolant could condense under its own weight, with little mechanical help except from a pump, similar to air over the water column in the Taylor compressor. It was an idea that eventually became integrated into the concept of his chiller, replacing the static charge of the water column with the centrifugal compressor. In his important February 1926 paper, "Centrifugal Compression Applied to Refrigeration," Willis Carrier discusses the concept of static charge and credits it as an example for understanding the process where compression is produced by a gravitational column (Figure 1).
Condensation by means of static, based on the height of the gas column of the condenser which was a concept that led to the development of the centrifugal cooler.
In this diagram the pump pushes the theoretical coolant to the evaporator. It changes its state to steam in the evaporator and condenses at the bottom of the system, due to the static charge. Obviously this is not a practical system, however, the concept was easy to understand and you can intuit the replacement of static charge by the compressor.
The concept and theory were simple. The hardest part is making it work in the real world. Two main components were required, the compressor and the refrigerant. At that time, there were no suitable refrigerants, some had a future, but all had toxicity or flammability problems. Propane was once marketed as the safest alternative to the most common refrigerants of the time.
Various refrigerants or "volatile fluids," to use the terminology of the time, were exactly that, highly volatile. Vapor compression cooling had been operating since 1830 in the odd experiment. The list of compounds to use was extensive and after extensive testing a compound called dichloroethylene was selected by Carrier as the best.
He found a manufacturer in Germany that would manufacture what would essentially be a cleaning fluid in a certain quantity. Other studies indicated that it was composed of two different isomers and the product was extensively refined for more stable and predictable performance, however, it was highly flammable. The vapors moved like gasoline to an ignition source and if ignited, would produce deadly byproducts. Today it would be classified as a B3 refrigerant, based on the ANSI/ASHRAE standard 34-2001, Designation and Safety Classification of Refrigerants. This would be the most toxic and flammable classification. It was the best technology available back then despite its disadvantages.
The next component was the centrifugal compressor. Carrier at the time did not have the manufacturing capacity to develop its own compressor, so the search for a suitable manufacturer began. Air compressors of this type were not new and four potential European suppliers were evaluated. The C.H. Jaeger Company, from Leipzig, Germany, was chosen. After World War I, Germany was fertile ground for cheap manufacturing and Carrier and its team took advantage of this opportunity. The C.H. Jaeger Company had begun operations in 1898 as a foundry. The company had begun manufacturing centrifugal fans in 1905 and its first centrifugal compressor in 1910. They continued to manufacture compressors for Europe and later for the German war effort in World War II. Jaeger continued to operate in East Germany until reunification when the firm was privatized again. Jaeger continues to manufacture centrifugal compressors today, as part of PGW Turbo, for the water treatment and industrial markets.
Many modifications had to be made to the compressor when it arrived at Carrier's new jersey workshop in 1920 or 1921. New lubrication systems operating in a dichloroethylene atmosphere were required and the shaft seal was a big problem. The problem of the seal was solved by using a special bellows. When the compressor stopped, the springs kept the face of the seal tight to the seat. When the bellows worked, it was pressurized by lifting the face of the seat seal and pressurizing that area with oil from the lubrication pump. An effective seal solved an annoying problem. Carrier patented the centrifugal cooling machine in 1921. That development progressed to a point where the machine could be introduced to the market in May 1922. The chiller was presented at a meeting of ASRE, the American Society of Refrigeration Engineers, precursors of ASHRAE. Many members of the Carrier team were members of the society, four of the seven founding members of the Buffalo Forge team were members of ASRE or ASHVE (American Society of Heating and Ventilation Engineers). And presidents of these associations over the years.
The presentation of the centrifugal chiller would be for 300 engineers at Carrier's workshop in New Jersey. To improve the presentation (and ensure attendance) a boxing match was prepared. "During Carrier's opening remarks, a loud noise like machinery was felt through the wall. Carrier later confessed that it was a terrible feeling that overwhelmed him when he heard a long noise of friction between two metal pieces. He thought the compressor engine had broken into pieces. Beads of sweat rolled down his forehead and his hands were wet but he kept talking, pretending to have heard nothing. Irvine (Lyle of the old Buffalo Forge), who was sitting at the back of the room, calmly walked out of it. He came back immediately and gave me a sign that everything was fine. Lyle later told me that the terrible noise had occurred because they had dragged a large metal table on a rough cement floor. No special sound effect could have so accurately mimicked the disintegration of an impeller." The compressor was of the horizontal "split case" type and all Jaeger compressors had horizontal suction and discharge. Many of these compressors were directly connected with 3600 rpm squirrel cage engines without using transmission, some prototypes used turbines. As production grew, they were manufactured in four, five and six stages and in five different sizes (Figure 2.)
Figure 2 (a). Old arrangement of the cooler components, showing the compressor on the condenser and horizontal corrections of suction and discharge. Information provided by Carrier.
Most of the production machines were the so-called sub base type in which the compressor was mounted on a short and low condenser, while the evaporator was elevated. The evaporator was not of the flooded type and used a tray for the distribution of the flow of the coolant over the tubes. The construction of the evaporator would be unrecognizable today.
The evaporator was multi-step, with removable heads and tubes 5/8" (16 mm) in diameter. The hull was cast iron with reinforced rim. The permanent joints were made of lead and asbestos and gaskets were used throughout. The tubes and mirrors were constructed of "Admiralty" bronze heated to the required temperature of the design. The sub assemblies were tested hydrostatically and with vacuum and pressure tests before shipment. The capacitors were essentially identical. Machines were assembled into the project.The lubrication system was simple, but very effective. It consisted of an oil pump with bronze tubes. There was an oil filter before the shaft seal. The bearings were not pressure lubricated, but were equipped with handles or rings of "babbit" metal (anti-friction metal). The bearings were split and had removable hulls. In newer compressor models from 1925, the engine-side bearings were removed from the refrigerant atmosphere, but in 1926 they were changed back to their original position, which remained for many years of compressor production.
The liquid pump does not exist today. This pump was used to circulate liquid refrigerant in the evaporator and usually had a glycerin seal with multi-layer packing. This pump circulated liquid coolant from the base to the top of a distribution tray. From this tray, the coolant circulated downward, through the tubes, cooling the water circulating inside the tubes. There was also an "evacuator" in the evaporator that would serve as a purge unit to remove non-condensable gases (air). Different types of evacuators were developed as the designs of the liquid coolers changed. An acceptable leak was 1" (249 Pa) of loss vacuum in 24 hours.
Figure 2 (b) (right) More modern arrangement of components. Both machines used methylene chloride and gas flow control was added to the compressor. Information provided by Carrier.
Photo 1. Reuben Trane, left, and associates look at the Turbovac prototype. This was the cover of the 1939 sales catalog, listing some facilities.
The first installation of a production line chiller was for an industrial application. The industry pushed the development of the chiller, not the office building market. The new machine could be applied in various conditions, using different combinations of impellers and sizes (diameters).
Technology grew rapidly. The first production machine was installed at Stephen F. Whitman and Sons of Philadelphia, a candy maker. The second went to another candy maker, William F. Schraftt and Sons of Boston, the following month. The prototype machine was sold to a pottery in Syracuse, N.Y.During 1925, the new line of "R" compressors was introduced. These were still manufactured by C. H. Jaeger and were similar to the previous ones, except for vertical suction and discharge (Photo 1). Carrier's design offered flexibility. The basic structure of the machine could be applied in air conditioning projects or in low temperature operations. The combinations of impellers, number of stages and exchangers (evaporators and condensers) gave the company a wide range of potential customers. It was an impressive engineering achievement.
The company grew rapidly because it offered large-scale delivery of temperature-controlled water and brine chillers that were offered to the paper industries, refineries, candy mills, and steel manufacturing. Other engineering companies noticed the situation and that's where the competition began.
In Europe, Brown-Boveri had a centrifugal cooler in operation using ammonia and in 1932 another chiller using ethyl bromide. In 1924 the centrifugal cooler became known to the public in department stores, cinemas and office buildings, other theaters and buildings had been cooled by refrigeration for several years, but the centrifugal cooler was simpler, more efficient and more reliable. The era of loading ice to cool cinemas was over. By 1930, 300 Carrier centrifugal coolers were installed in theaters. This type of cooler had advantages over the competition. Most ice water systems required a cooling plant with ammonia or co2 coolant. The water was normally cooled in a baudelot evaporator. This type of evaporator used an open tank with tubes or plates with coolant inside, the water was pumped through the tubes. Many applications required an insulated room for the baudelot evaporator. This custom-made system was bulky, difficult to operate, easy to freeze and required expert operation. The valves were manual, including the expansion valve. The oil coating on the walls of the heat exchanger was a normal problem but as a result of the solvent nature of dichloroethylene this was not a serious problem, as in the first centrifugal machines.
DEVELOPMENT
Early centrifugal chillers possessed many of the same advantages that today provide designers and engineers with a smaller area, reliable long-term operation, ease of installation, competitive pricing, simple operation and energy efficiency. The refrigerant problem continued, while dichloroethylene could be used without problems in chemical plants, its use in other applications was more problematic. So the search continued and methylene chloride was first used in 1926. Dichloroethylene only lasted four years. Methylene chloride (R-30) although it was better, is listed as a B-2 refrigerant, somewhat better than dichloroethylene. Nothing extraordinary, but, at least, it was not highly flammable. The Carrier team named this new refrigerant Carrene-1. It was still dangerous and difficult to manage, requiring special treatment and management. Technicians working with this refrigerant remember that it was extremely irritating and could be absorbed through the skin. It became clear that for the refrigeration industry to progress, new refrigerants were required. Very little or no competition existed in the following years and the Carrier company survived the Great Depression and still introduced a new compressor in 1933. This was a compressor of their own manufacture and they no longer imported the compressor from Germany. The "z" series was optimized for the new R-11 refrigerant. This system was able to incorporate an economizer for the first time to improve cycle efficiency and in the first series of reconditioning of centrifugal coolers, R-11 replaced dichloroethylene and methyl chloride (Carrene-1, R-30). The system had the same basic configuration as older machines and they still used the evaporator with emptyer.
In 1935, Ingersoll-Rand developed an interesting centrifugal cooler that used water as a coolant. This eliminated the need for the heat exchanger to cool the water. The speeds of the impellers and number of them were impressive at the time. The market penetration or success of this design is unknown. In 1936 Carrier's engineering department joined General Electric and produced a high-speed, single-stage centrifugal compressor. They called it the "G" compressor and it was unique for its small size and the use of a hermetically sealed motor. This model did not have great acceptance.
TURBOVAC TRANE
Alfred E. Stacey was chief research officer of the Carrier company from 1919 until he took the position of vice president, in charge of investigations in 1928 and vice president of engineering in 1931. Without a doubt, he had a great impact on the development of the centrifugal cooler. However, in 1935 he left Carrier and started his own business as a contractor/manufacturer. His company was called Buensod-Stacey. They manufactured and installed air washers and other air conditioning equipment for the textile and tobacco industry in the southeastern United States. They designed a unique, airtight cooler, but lacked the plants for the manufacture and development of the cooler. At the same time, Trane de La Crosse, Wis, produced a successful line of "Fan Coil" and "Climate Changers". They were the authors of the important "Trane Air Conditioning Manual" that became over the years the industry standard. They didn't have a cooler and were in the process of designing one. Buensod – Stacey and Trane teamed up in 1937 to produce the first hermetic centrifugal cooler, suitable for wide distribution. Trane engineers developed the cooler in 1938 and introduced it in 1939.This machine used the new R-113 refrigerant and the unique design offered features that the competition did not have. It was smaller, easy to operate and install and quiet. The cooler had two cylinders, the condenser above and the evaporator below. Located at the end of the evaporator was an engine with a two-stage centrifugal compressor. It delayed the acceptance of the new design, because during the first year they only sold three machines. It was originally offered from 65 to 80 tons of capacity and was the basis for rapid growth in the following years.
COMPETENCE
In 1936 Carrier engineers began designing a new configuration of the centrifugal cooler to take advantage of the new R-12 and R-11 refrigerants. That machine was introduced in 1939 as the 17 M series and possessed the same configuration we have today, using hull and tube heat exchangers and constructed of steel and copper (special heat exchangers were offered for industry). The compressor that faced next to the condenser and evaporator, with electric motor and transmission or turbine, was manufactured until a few years ago. Carrier had an exhibit at the 1939 World's Fair in New York that was shaped like an igloo with 12.2 m high thermometers showing the temperatures inside the building and outside. Appropriately next door was the DuPont pavilion. Without the advent of Freon refrigerants in 1931, the refrigeration and air conditioning industry would not have been able to develop (Photo 2).
Photo2. The Carrier "Igloo" at the New York World's Fair in 1939, had two thermometers 45 feet (12.2 m) high, showing indoor and outdoor temperatures.It was also the year in which the competition was developed using industrial-type centrifugal compressors with open engines from York and Worthington, to operate with R-11. Carrier was no longer the only supplier that had industrial centrifugal chillers. More research is required to write about these early machines.
What happened to the first prototype compressor that was built in Carrier's new jersey workshop? After operating for several years in a ceramics company in New York, it was donated to the Smithsonian Museum in Washington D.C. In 1960 my father took us to the capital to visit. We took a special trip to the Smitnsonian museum to see the compressor, so my father could take a picture in front of it.
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